I have a Chrysler 140 in the shop because it is over heating. The mechanic has replaced the water pump. The problem persists. He ran solvent through the ports but this did not help. He says there is only 2 to 3 pounds of water pressure at 2500 rpms and should be around 15. There is not significant water pressure at low rpm to cool the engine. He is suggesting a larger housing for a heavy-duty pump. Any ideas for a housing that will interchange on this engine? Or any other possible solutions to this problem? Thanks!